Polyhydroxy polyurethane resins, which make use of carbon dioxide as a production raw material, are known for some time (see, for example, Patent Documents 1 and 2). Under the current situation, however, the development of their applications has not moved ahead, because these polyhydroxy polyurethane resins are evidently inferior in characteristics to polyurethane-based resins comparable as high-molecular compounds of similar type.
On the other hand, the global warming phenomenon which can be considered to be attributable to the ever-increasing emission of carbon dioxide has become a worldwide problem in recent years, and a reduction in carbon dioxide emissions has arisen as a critical issue for the entire world. The change to renewable resources such as biomass and methane has also become a worldwide technological trend from the viewpoint of the problem of exhaustible fossil resources (petroleum) (for example, Non-patent Documents 1 and 2).
Under the above-described background, the present inventors put a fresh look on the above-described polyhydroxy polyurethane resins, and have come to realize that the provision of a technology capable of enabling the development of applications of these resins is very effective. Described specifically, carbon dioxide which is a raw material for such polyhydroxy polyurethane resins is a readily-available and sustainable carbon resource, and the provision of a technology that makes effective use of a plastic, in which carbon dioxide used as a raw material is fixed, is considered to find utility as an effective means for resolving serious problems such as warming, resource depletion and the like which the earth confronts in recent years. The use, if possible, of a polyhydroxy polyurethane resin, which contains carbon dioxide fixed therein, in the below-described products with imitation leathers or skin materials employed therein will be extremely effective because these products are used in large quantities.
(Imitation Leathers)
Conventionally, imitation leathers have been used in pouches, bags, shoes, furniture, clothing, vehicle interior trim materials, electric appliances, and the like. As resins for these imitation leathers, polyurethane-based resins are widely used. The term “imitation leather” is a generic term for leather-like products manufactured resembling natural leathers. In general, imitation leathers can be roughly divided into artificial leathers, synthetic leathers, and vinyl chloride leathers.
Artificial leathers have a structure closest to that of natural leathers among imitation leathers, and use a non-woven fabric as a base fabric. As a process for the production of a general artificial leather, there is a process to be described hereinafter. After a nonwoven fabric is first impregnated with a solution of a polyurethane-based resin in dimethylformamide (hereinafter abbreviated as “DMF”), the polyurethane-based resin is solidified and dried into a porous form by wet-process film formation (submerged solidification). Subsequently, its surface is further coated with a polyurethane-based resin or provided with a laminated layer of the polyurethane-based resin to present a smooth tone, or its surface is ground to raise fibers such that a suede tone is presented.
On the other hand, synthetic leathers use, as a base fabric, a fabric such as a woven fabric or raised blanket, and in general, are roughly divided into dry-process synthetic leathers and wet-process synthetic leathers depending upon a difference in production process. For the production of a dry-process synthetic leather, there are two processes, one being to coat a polyurethane-based resin directly on a base fabric and to dry it, and the other to coat a polyurethane-based resin on a sheet of release paper, to dry the polyurethane-based resin into a film, and then to bond the film and a base fabric together with an adhesive. On the other hand, a wet-process synthetic leather can be produced by impregnating or coating a base fabric with the above-mentioned solution of the polyurethane-based resin in DMF and then subjecting the polyurethane-based resin to submerged solidification and drying to form a porous layer. Further, the surface of the synthetic leather obtained by the dry process or wet process as described above is coated or laminated with a polyurethane-based resin to provide a layer such that a smooth tone is presented, or the surface is ground to raise fibers such that a suede tone is presented.
As mentioned above, the reduction of carbon dioxide emissions has become a critical worldwide issue. In the field of imitation leathers, more and more makers are also positively working on environmental measures, resulting in a move toward forming imitation leather products by using materials excellent in environmental conservation properties. A great deal of research is hence under way, for example, to reduce VOC (volatile organic compound) emissions as much as possible by using polyurethane-based resins, which are dispersible or emulsifiable in water-based media, in place of polyurethane resins that use an organic solvent, or to use plant-derived raw materials from the viewpoint of carbon neutral. However, the resulting imitation leather products are still different in performance compared with the conventional products, and therefore, are considered to have problems for practical applications. Moreover, these approaches are still insufficient in respect to the realization of the conservation of the current environment on the global scale (Patent Documents 3 to 5).
(Skin Materials Made of Thermoplastic Polyolefin Resins)
Concerning vehicle interior trim materials (instrument panels, door trims, etc.) and home electric appliance components and parts, the recycling of their constituent members is strongly desired to decrease waste materials as much as possible after use in view of the worsening garbage-related problems and environment-related problems in recent years. From this viewpoint, thermoplastic polyolefin resins, for example, polypropylene resin (hereinafter abbreviated as “PP resin”), ABS resin, AS resin, polyolefin-based thermoplastic elastomers (hereinafter abbreviated as “TPO resins”) and the like are used as materials for forming the above-described members. However, these thermoplastic polyolefin resins are inferior in surface adhesiveness, scratch resistance, abrasion resistance and chemical resistance in comparison with vinyl chloride resin and the like which have been conventionally used, and therefore, are required to apply coatings for providing improved performance. To realize artistry for giving a high-grade appearance, or concerning car interior trim materials in particular, it is necessary to consider not only the artistry but also an attention to anti-glare properties for drivers. Accordingly, it is also practiced to apply various coatings to the surfaces of thermoplastic polyolefin base materials such that top coat layers are formed to impart functionality and the thermoplastic polyolefin base materials are converted to still better skin materials made of the thermoplastic polyolefin resins.
Conventionally proposed is a method that uses a chlorinated polypropylene resin, which has good adhesiveness to a polyolefin-based resin such as PP resin or a TPO resin used as a base material, in a coating formulation to be employed in the above-described coating applications. Specifically, there have been proposed, for example, a method that uses a coating formulation containing a chlorinated polypropylene-modified acrylic resin as a binder resin and a matting agent such as an inorganic extender pigment (silica or talc) or acrylic resin particles added thereto, and a method that applies a chlorinated polypropylene-based primer and applies on the primer a coating formulation containing a polyester resin or polyurethane resin.
Recently, there is an increasing consciousness towards environmental problems. More and more makers are, therefore, positively working on environmental measures, resulting in a move toward forming such products by using materials excellent not only in functionality but also in environmental conservation properties. Active research is hence under way, for example, to avoid choosing specific solvents (toluene and the like) from organic solvents for use in the above-described coating formulations or to use water-based resins instead of organic solvents for reducing VOC (volatile organic compound) emissions as much as possible. However, these approaches are still insufficient for the realization of the conservation of the current environment on the global scale (see Patent Documents 6 to 8). As the reduction of carbon dioxide emissions has become a critical worldwide issue as mentioned above, the development and use, if possible, of a material making use of carbon dioxide as a raw material will be extremely effective.